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Nagano-shi, Japan

Komatsu T.,Komatsuseiki Kosakusho Co. | Matsumura T.,Tokyo Denki University | Torizuka S.,Japan National Institute of Materials Science
International Journal of Automation Technology | Year: 2011

The cutting processes of ultra fine grain stainless steels are compared to that of normal grain steel in microscale cutting with a single point tool made of single crystal diamond. Cutting force is measured with oscillation in the dynamic component. Vibration in cutting force is reduced with the grain size. Shear angles are measured to discuss the cutting process with changes in depth of cutting. The large shear angle is observed when the grain size becomes small. The surface finish is also improved when the ultra fine grain steel is machined.

Zheng Q.,Tokyo Metroplitan University | Shimizu T.,Tokyo Metroplitan University | Shiratori T.,Komatsuseiki Kosakusho Co. | Yang M.,Tokyo Metroplitan University
Materials and Design | Year: 2014

Pure titanium (Ti) is often used for microparts in biomedical devices and implants. Microforming is a promising technology for the manufacture of microparts. Owing to the occurrence of size effects in microforming, the material flow is nonhomogeneous and the process parameters exhibit considerable scattering. Heat-assisted microforming is an effective process for solving these problems. To improve the heating rate, the resistance heating method has been introduced into the microforming process. To design an effective resistance-heating-assisted microforming process, the relationship between the electric current and the flow stress of the material should be determined.To achieve this, a tensile testing system incorporating the resistance heating method is developed in this study. The tensile properties of 0.05-mm-thick pure Ti foils are investigated by performing uniaxial tensile tests at elevated temperatures. The tensile tests are carried out at different angles (0°, 45°, and 90°) relative to the rolling direction, at various temperatures from room temperature (298K) to 723K, and under different strain rates from 10-4 to 10-1s-1. To contribute to the design of the resistance-heating-assisted microforming process, the effect of the temperature and electrical current density on the material properties of ultrathin pure Ti foils is discussed. A constitutive model based on the Fields-Bachofen (FB) equation is derived to describe the flow stress of ultrathin pure Ti under different forming conditions. The effect of the electrical current density on the work hardening and strain rate sensitivity is included in the derived constitutive model. The good agreement between the calculated and experimental results confirms the feasibility of the proposed constitutive model for resistance-heating-assisted microforming. © 2014 Elsevier Ltd.

Komatsu T.,Komatsuseiki Kosakusho Co. | Yoshino T.,Tokyo Denki University | Matsumura T.,Tokyo Denki University | Torizuka S.,Japan National Institute of Materials Science
Procedia CIRP | Year: 2012

The crystal grain size of the work material is relatively large compared to the removal depth in micro-scale cutting. Therefore, the micromilling requires the small crystal grains in the material to machine accurate products in a stable manner. The study investigates the effect of crystal grain size on the cutting process in micromilling. The crystal grains of stainless steel in this study are downsized to an average size of 1.5m by repetition of material forming and phase transformation. The milling processes of ultra fine-grained steels were compared with those of normal grain steels. The milling tests were performed to measure the cutting force and the surface quality. The force component ratio of the ultra fine-grained steel is higher than that of the normal grain steel. The shearing force decreases in cutting of the ultra fine-grained steel; meanwhile, the friction and/or the indentation forces increase. Burr formation can be reduced with the crystal grain size. In cutting of the normal grain steel, thrust component in the cutting force suddenly drops near the end of the grooves and a large burr is left on the edge of the groove. © 2012 The Authors.

Japan National Institute of Advanced Industrial Science, Technology and Komatsuseiki Kosakusho Co. | Date: 2015-10-13

A method for bonding stainless steel members includes: contacting a first stainless steel member with a second stainless steel member that has a strain exceeding 50% reduction; and heating the first and second stainless steel members to a re-crystallization initiation temperature or higher, after the contacting.

Katoh M.,Japan National Institute of Advanced Industrial Science and Technology | Sato N.,Japan National Institute of Advanced Industrial Science and Technology | Shiratori T.,Komatsuseiki Kosakusho Co. | Suzuki Y.,Komatsuseiki Kosakusho Co.
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2016

Diffusion bonding at low temperature is a necessary process for the manufacturing of metal MEMS (Micro-Electronic-Mechanical Systems) such as, in the case of metal micro-pump that requires a high proof strength. Metals with severe plastic deformation having high mobility grain boundaries are known to bond at low temperatures. We then simultaneously carried out recrystallization and solid phase diffusion bonding of the metals. In this paper, we have confirmed a reduction in the diffusion bonding temperature in severe plastic-deformed SUS304 and SUS316L as compared to the case of heat treated solutions. Especially the bonding temperature was decreased considerably in SUS304 having strain-induced martensite.

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